The invention relates to moisture curable hot melt sealants.
Insulating glass assemblies such as insulating glass units and insulating sash assemblies often include a pair of glass sheets maintained in a fixed spaced relation to each other by a spacing and sealing structure that extends around the periphery of the inner facing surfaces of the glass sheets to define a sealed and insulating space between the glass sheets. In the case of insulating sash assemblies, the glass panes are adhered to a frame. The glass sheets are usually attached to the structure by a sealant or adhesive composition. The sealant or adhesive composition is also used to seal the edges of the insulating sash assembly so as to establish a barrier that prevents moisture from penetrating into the interior of the assembly. Insulating sash assemblies are described, e.g., in U.S. Pat. No. 6,286,288.
Sealant compositions are also used to bond an insulating glass assembly, e.g., an insulating glass unit, to a frame. This process is often referred to as xe2x80x9cback bedding.xe2x80x9d Back bedding is discussed in, e.g., U.S. Pat. Nos. 6,286,288 and 5,856,404 and incorporated herein. In the fabrication of door and window units back bedding sealants are often used to seal and bond panes of glass and insulating glass units to retain the pane or the unit in position within a frame, to provide a weather proof seal, to reinforce the structural strength of the assembly, or a combination thereof.
Variables that arise in bonding two substrates of different materials, such as bonding a glass substrate to a polymer substrate, include the different coefficients of thermal expansion and contraction associated with the two materials. The differences in these coefficients can cause stresses to be exerted on one or more of the substrates when the assembly experiences a change in temperature, which can torque polymer substrates and cause fractures in glass substrates.
Two common classes of sealants used in the insulating glass industry include chemically curing, thermoset compositions, and thermoplastic, one-part hot melt butyl-type compositions. Chemically curing systems often include liquid polysulphides, polyurethanes, mercaptan-modified polyether polyurethanes and silicones. Thermoplastic compositions, which are also referred to as xe2x80x9cnon-curing systems,xe2x80x9d are often polyisobutylene-polyisoprene copolymer rubber-based hot melt compositions.
Chemical curing thermoset sealants are usually two-component systems in which the components are combined, at room temperature, just prior to application. The sealants have low initial green strength and require cure time prior to handling. The slow cure can increase manufacturing time and costs.
Non-curing hot melt systems generally set faster and can overcome the disadvantage of having a slow cure time, but hot melts are more susceptible to fluctuations in ambient temperature and may soften with high temperatures or stiffen with cold and do not develop as high ultimate bond strengths in comparison to curing systems. When insulating glass assemblies constructed with thermoplastic sealants are placed under load and temperature, the thermoplastic sealant may flow or deform to relieve the load. In addition, thermoplastic sealants are often applied at very high temperatures, e.g., in excess of 300xc2x0 F.
Other sealant compositions that have been developed include a one part sealant that includes thermoplastic hot melt resin and an atmosphere curing resin capable of polymerizing upon exposure to ambient atmosphere.
In one aspect, the invention features a moisture curable hot melt sealant composition that includes a polyurethane prepolymer having isocyanate functional groups, silane functional groups, or a combination thereof, a reactive plasticizer capable of reacting with at least one of the polyurethane prepolymer and itself, and thermoplastic polymer.
In one embodiment, the polyurethane prepolymer includes silane functional groups. In other embodiments the polyurethane prepolymer includes isocyanate functional groups.
In some embodiments, the composition includes from about 5% by weight to about 50% by weight the polyurethane prepolymer, from no greater than 20% by weight the reactive plasticizer, and from about 5% by weight to about 80% by weight the thermoplastic polymer. In other embodiments, the composition includes from about 10% by weight to about 40% by weight the polyurethane prepolymer, from about 2% by weight to about 15% by weight the reactive plasticizer, and from about 10% by weight to about 70% by weight the thermoplastic polymer. In another embodiment, the sealant includes from about 15% by weight to about 35% by weight the polyurethane prepolymer, from about 3% by weight to about 10% by weight the reactive plasticizer, and from about 15% by weight to about 60% by weight the thermoplastic polymer.
In one embodiment, the reactive plasticizer has a molecular weight of from about 300 g/mole to about 10,000 g/mole. In other embodiments, the reactive plasticizer has a molecular weight of from about 500 g/mole to about 6,000 g/mole.
In some embodiments, the polyurethane prepolymer includes the reaction product of polyester polyol, polyisocyanate; and monofunctional alcohol.
In one embodiment, the polyurethane prepolymer includes the reaction product of polyester polyol, polyisocyanate, monofunctional alcohol and hydrogen active organofunctional silane.
In some embodiments, the hydrogen active organofunctional silane includes amino-alkoxysilane, mercapto-alkoxysilane, or a combination thereof.
In another embodiment, the hydrogen active organofunctional silane includes N-methyl-3-amino-2-methylpropyltrimethoxysilane, N-ethyl-3-amino-2-methylpropyltrimethoxysilane, N-ethyl-3-amino-2-methylpropyldiethoxysilane, N-ethyl-3-amino-2-methylpropyltriethoxysilane, N-ethyl-3-amino-2-methylpropylmethyldimethoxysilane, N-butyl-3-amino-2-methylpropyltrimethoxysilane, 3-(N-methyl-3-amino-1-methyl-1-ethoxy)propyltrimethoxysilane, N-ethyl-4-amino-3,3-dimethylbutyidimethoxymethylsilane, N-ethyl-4-amino-3,3-dimethylbutyltrimethoxysilane, bis-(3-trimethoxysilyl-2-methylpropyl)amine, N-(3xe2x80x2-trimethoxysilylpropyl)-3-amino-2-methylpropyltrimethoxysilane, N-(n-butyl)aminopropyltrimethoxysilane, or a combination thereof.
In one embodiment, the monofunctional alcohol has from 12 to 20 carbon atoms.
In some embodiments, the reactive plasticizer includes silyl-terminated polyether. In other embodiments, the reactive plasticizer includes alkoxysilyl reactive groups. In another embodiment, the reactive plasticizer is selected from the group consisting of aldimines, ketimines, oxazolidines, dioxolanes, and combinations thereof.
In another embodiment, the composition exhibits an initial lap shear of at least 10 psi. In some embodiments, the composition exhibits an open time of at least 60 seconds. In other embodiments, the composition exhibits a softening temperature of no greater than 50xc2x0 C.
In another embodiment, the sealant composition has a glass transition temperature of less than xe2x88x925xc2x0 C. In one embodiment, the sealant composition has a glass transition temperature of less than xe2x88x9225xc2x0 C. In some embodiments, the composition exhibits a viscosity of from about 150,000 centipoise to about 400,000 centipoise at 230xc2x0 F. In other embodiments, the composition exhibits a lap shear of at least 80 psi after three weeks at 23xc2x0 C. and 50% relative humidity.
In other embodiments, the composition, after cure, exhibits an elongation of at least 200%.
In one embodiment, the composition, after cure, exhibits a tensile strength of at least 100 psi. In some embodiments, the composition, after cure, exhibits a modulus at 100% elongation of no greater than 300 psi. In another embodiment, the composition, when in the form of a cured 60 mil film, exhibits a moisture vapor transmission rate no greater than 10 g/m2/day.
In other embodiments, the composition further includes at least one of tackifying agent, non-reactive plasticizer and silane adhesion promoter.
In some embodiments, the thermoplastic polymer includes ethylene vinyl acetate. In other embodiments, the thermoplastic polymer is selected from the group consisting of polyolefins, polyesters, polyacrylates, polymethacrylates, polyacrylamides, polyacrylonitriles, po)yimides, polyamides, copolymers of vinyl alcohol and ethylenically unsaturated monomers, polyvinyl chloride, polysiloxanes, polyurethanes, polystyrene, and combinations thereof. In another embodiment, the thermoplastic polymer includes thermoplastic elastomer selected from the group consisting of polyetheramide copolymers, styrene-butadiene-styrene copolymers, styrene-isoprene-styrene copolymers, styrene-ethylene-butylene-styrene copolymers, styrene-ethylene-propylene-styrene copolymers, butyl rubber, polyisobutylene, and combinations thereof.
In another aspect, the invention features a multipane glass assembly that includes a first glass pane, a second glass pane, a spacer, and a sealant composition including the reaction product of a moisture curable hot melt sealant composition disclosed herein, and thermoplastic polymer, the first glass pane and the second glass pane being bonded to the structural frame through the sealant composition.
In one embodiment the multipane glass assembly includes an insulating glass unit that includes a first glass pane, a second glass pane, a spacer, and a first sealant composition, the first glass pane being bonded to a first surface of the spacer through the first sealant composition, the second glass pane being bonded to a second surface of the spacer through the first sealant composition, a frame and a second sealant composition, the insulating glass unit being bonded to the frame through said second sealant composition, the second sealant composition including a moisture cured sealant composition including the reaction product of a polyurethane prepolymer including isocyanate functional groups, silane functional groups, or a combination thereof, reactive plasticizer capable of reacting with at least one of said, polyurethane prepolymer and itself, and thermoplastic polymer.
In other aspects the invention features a polyurethane prepolymer that includes the reaction product of polyester polyol, polyisocyanate, and monofunctional alkyl alcohol having from 12 to 16 carbon atoms. In one embodiment, the polyol is amorphous. In other embodiments, the polyol has a glass transition temperature less than 0xc2x0 C. In some embodiments, the polyol is hydrophobic. In another embodiment a moisture curable hot melt sealant composition includes the prepolymer. In one embodiment the sealant composition further includes thermoplastic polymer. In other embodiments, the sealant composition further includes reactive plasticizer.
In still other aspects, the invention features a method of bonding a first substrate to a second substrate, the method including contacting a first substrate with a moisture curable hot melt sealant composition disclosed herein, and contacting the sealant composition with a second substrate. In one embodiment, the first substrate includes at least one of glass and polymer. In other embodiments, the second substrate includes at least one of glass and polymer.
In other aspects, the invention features a method of making an insulating glass assembly, where the method includes contacting a first substrate with a moisture curable hot melt sealant composition disclosed herein and contacting the sealant composition with a second substrate.
In another aspect, the invention features a moisture curable hot melt sealant composition that includes a moisture curable polymer, reactive plasticizer capable of reacting with at least one of said moisture curable polymer and itself, and a thermoplastic polymer.
The invention features a hot melt moisture curable sealant composition that exhibits good adhesion to glass and plastic, i.e., polymer-based substrates, and good moisture barrier properties, i.e., works to prevent or inhibit the penetration of moisture into the chamber sealed thereby. The sealant also exhibits good adhesion retention to glass, plastic and metal substrates under weathering conditions, good flexibility at low temperatures, and good creep resistance (i.e., holding power) at elevated temperatures. The sealant also generates little to no volatile organic compounds and exhibits low modulus, good elastic recovery and an ability to dissipate stress.
The sealant can be applied at relatively low application temperatures while maintaining a useful open time and suitable handling strength.
The invention also features a polyurethane prepolymer that is tacky and exhibits good flexibility, good barrier properties, good water resistance and good ultraviolet light resistance.
Other features and advantages will be apparent from the following description of the preferred embodiments and from the claims.